JOC Year-in-Review, 1984

Transcription

1 Baran Lab Group eting JC Year-in-eview, 198 Y oshihiro Ishihara Statistics for J. rg. Chem. 198, Volume 9, Issues 1-26: 1313 Papers 1 erbert C. Brown 8 Albert Padwa 8 Leo A. Paquette 7 Dale L. Boger 7 George A. lah... Samuel J. Danishefsky 1 lias J. Corey Problems of the Day: C 2 1 C 2 C 2 (Major) + C 2 C 2 (Minor) Syntheses discussed: Δ 2 Δ 3 2 C C epi-Desosamine 2 C C 2 Cyanobacterin 2 Alternatively: 1 2?? 1 2 chanism and side product? (±)-Aphidicolin (±)-β-chamigrene 2 5? Perhydropyrido[2,1,6-de]quinolizines 2 5% TF (55 %) C 2 (Disclaimer: The proposed mechanism is neither discussed in the paper nor in the references, and thus the answer given is merely an opinion/suggestion.) 1

2 BaranLabGroupeting JC Year-in-eview, 198 Y oshihiro Ishihara Synthesis of 5-epi-Desosamine via a Stereoselective Intramolecular -Sulfinyl Diels-Alder Cycloaddition S. W. emiszewski,.. Whittle and S. M. Weinreb* J. rg. Chem. 198, 9, Total Synthesis and X-ay Structure Determination of Cyanobacterin T. -T. Jong, P. G. Williard* and J. P. Porwoll J. rg. Chem. 198, 9, a 1) BuLi, then i PrC 3 P C 3 s BuLi (2 eq) Br then, then C LiAl (68 %; 2 steps) (57 %) S 2 py, 0 C (80 %) 1) MgBr 2) Piperidine, t, reflux (90 %; 2 steps) S 2 ac, TFA (80 %) (C) n cat. Ts, Δ 1) TFA 2) 3 /Si 2, then Zn, Ac (70 %; 2 steps) 2 S 2 5-epi-Desosamine C 1) B 3 2) C 2 Br 2,aF 1) LDA, then excess LDA 2) 3, then Si 2 Separation (72 %; 2 steps; dr :1) g 2+ 6-endo-dig (~100 %) 2) Mn 2 1) a, (t) 2 P C 2 C 2 t 2) 2,Pd/C 3) a Ag + ;5-exo-dig (90 %)??? Cyanobacterin 3 2

3 BaranLabGroupeting JC Year-in-eview, 198 Total Synthesis of (±)-Aphidicolin and (±)-β-chamigrene.. Ireland,* W. C. Dow, J. D. Godfrey and S. Thaisrivongs J. rg. Chem. 198, 9, C 2 C 2 C 2 (±)-β-chamigrene, 2,sens. 1) DIBAL 2) 3 P=C 2 (95 %; 2 steps) 1) BuLi, then isoamyl nitrite, then 2) 2 (~25 %; 2 steps) C 2 16, t 2 C 2 C 2 2, a C 2 C 2 ydroquinone, Δ (96 %; dr 2.6:1) 150 C (8 %) C 2 C 2 C 2 16 Si 2 TBS 1) s 2) Ts, 2 C() 2 3) TBAF (92 %; 3 steps) 1) K, then, then Pd(Ac) 2 2) t 3, (C) n, S, t (70 %; 2 steps) 1) Li, then C (g), then Ac 2) L-Selectride 3) (9 %; 3 steps) 2 C C 2 S C 2 1) DIBAL 2) TBS (9%; 2 steps) 1) BuLi, then 2 P() 2 2) Li, 2 3) PPTS, acetone (82 %; 3 steps) Li, 3 then (90 %) (±)-Aphidicolin 3

4 BaranLabGroupeting JC Year-in-eview, 198 Stereo- and egioselective Total Synthesis of the ydropyrido[2,1,6-de]quinolizine Ladybug Defensive Alkaloids.. Mueller,* M.. Thompson,. M. DiPardo J. rg. Chem. 198, 9, ) +,KC 2) S 3 / 2 S (80 %; 2 steps) 2 g(ac) 2,DTA (71 %) 2 1) 2,Pd/C 2) P 3,py (2 %; 2 steps) C Cr 3 (79 %) 2,Pd/C Ts (68 %) (~50 %) 2,Pd/C 190 C (97 %) B 3 u 2,aI B (67 %) (35-5 %) (dr ~92:8!) 3, 2,Pd/C (80 %) 10? g(ac) 2,DTA (83 %) B 10 verall idea: -DP then 2 2, a (69%)

5 BaranLabGroupeting JC Year-in-eview, 198 erbert C. Brown (Purdue U.) 1) ne-carbon extension into a carboxylic acid: J. r g. Chem. 198, 9, B 1) LiC() 2 2) 2 2,a 3 C J. Am. Chem. Soc. 1971, 93, ) LiC() 2 2 B' 2) 2 2,a J. Am. Chem. Soc. 1975, 95, Analogous reaction was unsuccessful with bis-boronic esters: 1) LiC() 2 1) LiC 3,TF B(') 2 B(S') 2 2) 2 2,a 2) 2 2,a Does not for m viaaboron-ate complex: Also: S' 1) LiC 3,TF B(S') Li 'S B C 2 2 2) 2, a, Δ 2) nantioselective allylation: J. rg. Chem. 198, 9, β-carene 1) B 2 2) MgBr B B-Allyldiisocaranylborane S' S' 3) LiB reduction of olefins in the presence of esters: J. rg. Chem. 198, 9, ; C-C 2 -(C 2 ) 9 -C 2 t 1) LiB (2 eq) 2) 2 2,a 2 C=C-(C 2 ) 9 -C 2 t 1) LiB (3 eq) 2) 2 2,a lefin-assisted ester reduction: Deliberately add an ester to reduce olefins: 1) LiB (3 eq), tac (1 eq) 2) 2 2,a 1) LiB (3 eq), tac (1 eq) 2) I 2,a 3 C-C 2 -(C 2 ) 9 -C 2 Slow reaction -C 2 -C 2 -(C 2 ) 9 -C 2 Fast reaction 1 B ' I 2 1) LiB (3 eq), tac (1 eq) 2) 2 2,a ) Stereoselective cyclic ketone reductions: J. rg. Chem. 198, 9, K B B 9-BB- K C (72-80 %; % ee) [] (99:1 dr) ften better selectivities than Selectrides! [] 5

6 BaranLabGroupeting JC Year-in-eview, 198 Y oshihiro Ishihara Leo A. Paquette (hio State U.) 1) thylene ketene equivalents in [2+2] cycloadditions: J. r g. Chem. 198, 9, " 2 C C C " 2 C C 2 C ' 1) S 2 2) CS, S 2 TBAF C 2 2 C C 2 C ' ' Base TBAF C C 2 C 2) Trimethylsilyl cyclopropanes in synthesis: J. rg. Chem. 198, 9, ; ; S Br S 1) Mg 2) C 2 1) BuLi 2) TBS C 2 C 2 I 2 tzni TBS Li S aphthalene C 2 ' ' [Si] Y Y=-C 2 Br, -C 2 S, -P() 2, etc. Albert Padwa (mory U.) Generation of azomethine ylides from amides: J. r g. Chem. 198, 9, Δ WG uisgen J. Am. Chem. Soc. 1967, 89, WG WG WG ' ' CsF 3 BF Dale L. Boger (U. of Kansas) ' ' Vedejs J. Am. Chem. Soc. 1979, 101, CsF ' Studies in pyrrole synthesis using tetrazines: J. r g. Chem. 198, 9, ' DG =ster ' ' ' 1) Zn, Ac 2) a, Δ ' 6

7 BaranLabGroupeting JC Year-in-eview, 198 Cycloaddition eactions of Strained ing Systems. otochemistry of 1- enyl-2-carbomethoxy-3,3-dimethylcyclopropene A. Padwa* and G. D. Kennedy J. rg. Chem. 198, 9, C 2 C C lectronically excited triplet state generation via sensitized photolysis: C 2 1 C 2 C 2 (Major) + C 2 C 2 (Minor) (Pyrex-filtered) C 2 Δ 2 Δ 3?? 2 C C 2 lectronically excited singlet state generation via direct photolysis: C 2 C 2 C 2 o sensitizer a breaks chanism: xcited singlet, generates a vinyl carbene C- insertion C 2 migration C C 2 C 2 (9 %) (30 %) (20%) b a C 2 C 2 b breaks -C 2 migration? 2 C C 2 C- insertion C 2 Antibacterial Benzisoxazolones. An Unusual earrangement Product from o- itrostyrene xide en oute to the otolabile Carbonyl Protecting Group (o- itrophenyl)ethylene glycol W. Wierenga,* A. W. arrison, B.. vans and C. G. Chidester J. rg. Chem. 198, 9, 38-2 K 2 C 3 2, Δ (55 %) 2 True wonders: 2 Br 2 Al 3 (95 %) 2 K, dioxane 18-crown-6 (73 %) Br ab a (68 %) 2 5? 5% TF (55 %) 1 2 Deprotection involves light; chanism? C 2 7